Electrically heated smoking system having a liquid storage portion

ABSTRACT

An electrically heated smoking system includes a shell and a replaceable mouthpiece. The shell includes an electric power supply and electric circuitry. The mouthpiece includes a liquid storage portion and a capillary wick having a first end and a second end. The first end of the wick extends into the liquid storage portion for contact with liquid therein. The mouthpiece also includes a heating element for heating the second end of the capillary wick, an air outlet, and an aerosol forming chamber between the second end of the capillary wick and the air outlet. When the shell and mouthpiece are engaged or connected, the heating element is in electrical connection with the power supply via the circuitry, and a flowpath for air is defined from at least one air inlet to the air outlet via the aerosol forming chamber. In use, liquid is transferred from the liquid storage portion towards the heating element by capillary action in the wick. Liquid at the second end of the capillary wick is vaporized by the heating element. The supersaturated vapor created, is mixed and carried in the air flow from the at least one air inlet to the aerosol forming chamber. In the aerosol forming chamber, the vapor condenses to form an aerosol, which is carried towards the air outlet.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of application Ser. No.12/432,215, filed Apr. 29, 2009, entitled AN ELECTRICALLY HEATED SMOKINGSYSTEM HAVING A LIQUID STORAGE PORTION which corresponds to EuropeanApplication No. 08 251 579, filed Apr. 30, 2008, the entire content ofeach is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an electrically heated smoking systemfor receiving an aerosol-forming substrate. In particular, the presentinvention relates to an electrically heated smoking system for receivingan aerosol-forming substrate, in which the aerosol-forming substrate isa liquid.

A number of prior art documents, for example U.S. Pat. No. 5,060,671(commonly assigned, the entire contents of which are incorporated hereinby this reference thereto), U.S. Pat. No. 5,388,594 (commonly assigned,the entire contents of which are incorporated herein by this referencethereto), U.S. Pat. No. 5,505,214 (commonly assigned, the entirecontents of which are incorporated herein by this reference thereto),U.S. Pat. No. 5,591,368 (commonly assigned, the entire contents of whichare incorporated herein by this reference thereto), WO 2004/043175(commonly assigned, the entire contents of which are incorporated hereinby this reference thereto), EP-A-0 358 002 and WO 2007/131449, discloseelectrically operated smoking systems, having a number of advantages.One advantage is that they significantly reduce sidestream smoke, whilepermitting the smoker to selectively suspend and reinitiate smoking.

Other prior art documents, such as EP-A-0 295 122, EP-A-1 618 803 andEP-A-1 736 065, disclose electrical smoking systems which use a liquidas the aerosol-forming substrate. The liquid may be contained in acartridge which is receivable in a housing. A power supply, such as abattery, is provided, connected to a heater to heat the liquid substrateduring a puff, to form the aerosol which is provided to the smoker.

The electrically heated smoking systems of the prior art, includingthose described above, do have a number of advantages, but there isstill room for improvement. It is therefore an object of the inventionto provide an improved electrically heated smoking system.

SUMMARY OF SELECTED ASPECTS OF THE INVENTION

According to a first aspect of the invention, there is provided anelectrically heated smoking system comprising a shell and a replaceablemouthpiece, the shell comprising an electric power supply and electriccircuitry; the mouthpiece comprising a liquid storage portion, acapillary wick having a first end and a second end, the first endextending into the liquid storage portion for contact with liquidtherein, at least one heating element for heating the second end of thecapillary wick, an air outlet, and an aerosol forming chamber betweenthe second end of the capillary wick and the air outlet; wherein, whenthe shell and mouthpiece are engaged, the at least one heating elementis in electrical connection with the power supply via the circuitry, anda flow route for air is defined from at least one air inlet to the airoutlet via the aerosol forming chamber.

The at least one air inlet may be provided in the shell or in themouthpiece. In use, liquid is transferred from the liquid storageportion towards the heating element by capillary action in the capillarywick. When the heating element is activated, the liquid at the secondend of the capillary wick is vaporized by the heating element to form asupersaturated vapor. The supersaturated vapor is mixed and carried inthe air flow from the at least one air inlet to the aerosol formingchamber. In the aerosol forming chamber, the vapor condenses to form anaerosol, which is carried towards the air outlet into the mouth of auser.

The electrically heated smoking system according to the inventionprovides a number of advantages. Firstly, because the replaceablemouthpiece contains the at least one heating element, the liquid storageportion and the wick, all elements which are potentially in contact withthe liquid are changed when the mouthpiece is replaced. There will be nocross-contamination in the shell between different mouthpieces, forexample ones using different liquids. In addition, the liquid in theliquid storage portion is protected from oxygen (because oxygen cannotgenerally enter the liquid storage portion via the capillary wick) and,in some embodiments light, so that the risk of degradation of the liquidis significantly reduced. Therefore, a high level of hygiene can bemaintained. Secondly, the mouthpiece structure means that there is a lowrisk of leakage from the liquid storage portion, which is not the casefor many of the electrically heated smoking systems of the prior art.This prevents waste of the liquid, but also makes it difficult for anunauthorized user to access the liquid by dismantling the mouthpiece.Also, if the mouthpiece is replaced at suitable intervals, there islittle chance of the heating element becoming clogged with liquid.Finally, using a capillary wick extending between the liquid and theheating element allows the structure of the mouthpiece to be relativelysimple. There is preferably only one capillary mechanism in the system.

The at least one heating element may comprise a single heating element.Alternatively, the at least one heating element may comprise more thanone heating element, for example two, three, four, five, six or moreheating elements. The heating element or heating elements may bearranged appropriately so as to most effectively vaporize liquid at thesecond end of the capillary wick.

The at least one heating element preferably comprises an electricallyresistive material. Suitable electrically resistive materials includebut are not limited to: semiconductors such as doped ceramics,electrically “conductive” ceramics (such as, for example, molybdenumdisilicide), carbon, graphite, metals, metal alloys and compositematerials made of a ceramic material and a metallic material. Suchcomposite materials may comprise doped or undoped ceramics. Examples ofsuitable doped ceramics include doped silicon carbides. Examples ofsuitable metals include titanium, zirconium, tantalum and metals fromthe platinum group. Examples of suitable metal alloys include stainlesssteel, nickel-, cobalt-, chromium-, aluminum- titanium- zirconium-,hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-,manganese- and iron-containing alloys, and super-alloys based on nickel,iron, cobalt, stainless steel, Timetal and iron-manganese-aluminum basedalloys. In composite materials, the electrically resistive material mayoptionally be embedded in, encapsulated or coated with an insulatingmaterial or vice-versa, depending on the kinetics of energy transfer andthe external physicochemical properties required. Examples of suitablecomposite heating elements are disclosed in U.S. Pat. No. 5,498,855(commonly assigned, the entire contents of which are incorporated hereinby this reference thereto), WO 03/095688 and U.S. Pat. No. 5,514,630.

The at least one heating element may take any suitable form. Forexample, the at least one heating element may take the form of a heatingblade, such as those described in U.S. Pat. No. 5,388,594, U.S. Pat. No.5,591,368 and U.S. Pat. No. 5,505,214. Alternatively, the at least oneheating element may take the form of a casing or substrate havingdifferent electro-conductive portions, as described in EP-A-1 128 741,or an electrically resistive metallic tube, as described in WO2007/066374. Alternatively, the at least one heating element may be adisk (end) heater or a combination of a disk heater with heating needlesor rods. Alternatively, the at least one heating element may take theform of a metallic etched foil insulated between two layers of an inertmaterial. In that case, the inert material may comprise Kapton,all-polyimide or mica foil. Alternatively, the at least one heatingelement may take the form of a sheet of material, which may be rolledaround the second end of the capillary wick. The sheet may be made fromany suitable material, for example an iron-aluminum based alloy, aniron-manganese-aluminum base alloy or Timetal.

The sheet may be rectangular in shape, or may have a patterned shapewhich may form a coil-like structure when rolled around the second endof the capillary wick. Other alternatives include a heating wire orfilament, for example a Ni—Cr, platinum, tungsten or alloy wire, such asthose described in EP-A-1 736 065, or a heating plate.

In a preferred embodiment, the at least one heating element comprises acoil of wire surrounding the second end of the capillary wick. In thatembodiment, the wire is preferably a metal wire. Even more preferably,the wire is a metal alloy wire. The heating element may completely orpartially encircle the second end of the capillary wick.

The at least one heating element may heat the liquid at the second endof the capillary wick by means of conduction. The heating element may beat least partially in contact with the second end of the wick.Alternatively, heat from the heating element may be conducted to theliquid by means of a heat conductive element. Alternatively, the atleast one heating element may transfer heat to the incoming ambient airthat is drawn through the electrically heated smoking system during use,which in turn heats the liquid by convection. The ambient air may beheated before passing through the system. Alternatively, the ambient airmay be first drawn through the second end of the wick and then heated,as described in WO 2007/078273.

Preferably, the electric circuitry comprises a sensor to detect air flowindicative of a user taking a puff. The sensor may be anelectro-mechanical device. Alternatively, the sensor may be any of: amechanical device, an optical device, an opto-mechanical device and amicro electro mechanical systems (MEMS) based sensor. In that case,preferably, the electric circuitry is arranged to provide an electriccurrent pulse to the at least one heating element when the sensor sensesa user taking a puff. Preferably, the time-period of the electriccurrent pulse is pre-set, depending on the amount of liquid desired tobe vaporized. The electric circuitry is preferably programmable for thispurpose.

Alternatively, the electric circuitry may comprise a manually operableswitch for a user to initiate a puff. In that case, preferably, theelectric circuitry is arranged to provide an electric current pulse tothe at least one heating element when the user initiates a puff. Thetime-period of the electric current pulse is preferably pre-setdepending on the amount of liquid desired to be vaporized. The electriccircuitry is preferably programmable for this purpose.

Preferably, the at least one air inlet is in the shell. Alternatively,the at least one air inlet may be in the mouthpiece. In one embodiment,the at least one air inlet comprises two air inlets. Alternatively,there may be three, four, five or more air inlets. Preferably, if thereis more than one air inlet, the air inlets are spaced around the shellor around the mouthpiece. In a preferred embodiment, the electriccircuitry comprises a sensor to detect air flow indicative of a usertaking a puff, and the at least one inlet is in the shell, upstream ofthe sensor.

Preferably, the electric power supply comprises a cell contained in theshell. The electric power supply may be a lithium-ion battery or one ofits variants, for example a lithium-ion polymer battery. Alternatively,the power supply may be a nickel-metal hydride battery or a nickelcadmium battery or a fuel cell. In that case, preferably, theelectrically heated smoking system is usable by a smoker until theenergy in the power cell is used up.

Alternatively, the electric power supply may comprise circuitrychargeable by an external charging portion. In that case, preferably thecircuitry, when charged, provides power for a pre-determined number ofpuffs, after which the circuitry must be re-connected to the externalcharging portion. An example of suitable circuitry is one or morecapacitors or rechargeable batteries.

Preferably, the shell further comprises a puff indicator for indicatingwhen the heating element is activated. In the embodiment in which theelectric circuitry comprises a sensor to detect air flow indicative of auser taking a puff, the indicator may be activated when the sensorsenses air flow indicative of the user taking a puff. In the embodimentin which the electric circuitry comprises a manually operable switch,the indicator may be activated by the switch.

Preferably, the shell and mouthpiece are arranged to releasably locktogether when engaged.

Preferably, the liquid storage portion is not refillable. Thus, when theliquid in the liquid storage portion has been used up, the entiremouthpiece is replaced. Alternatively, the liquid storage portion may berefillable. In that case, the mouthpiece may be replaced after a certainnumber of refills of the liquid storage portion. Preferably, the liquidstorage portion is arranged to hold liquid for a pre-determined numberof puffs.

The liquid has physical properties, including viscosity, which allow theliquid to be transported through the capillary wick by capillary action.The liquid has a boiling point suitable for use in the electricallyheated smoking system: if the boiling point is too high, the heatingelement will not be able to vaporize liquid at the second end of thecapillary wick, but, if the boiling point is too low, the liquid mayvaporize even without the heating element being activated. The liquidpreferably comprises a tobacco-containing material comprising volatiletobacco flavour compounds which are released from the liquid uponheating. Alternatively, or in addition, the liquid may comprise anon-tobacco material. The liquid may include water, solvents, ethanol,plant extracts and natural or artificial flavours. Preferably, theliquid further comprises an aerosol former. Examples of suitable aerosolformers are glycerine and propylene glycol. Additional examples ofpotentially suitable aerosol formers are described in EP-A-0 277 519 andU.S. Pat. No. 5,396,911.

The liquid storage portion is preferably a container. For example, thecontainer may be a container such as that described in EP-A-0 893 071.Preferably, the liquid storage portion does not include any porousmaterials, so that there is only a single capillary mechanism (thecapillary wick) in the electrically heated smoking system. This keepsthe structure of the mouthpiece simple and the entire systemlow-maintenance. Preferably, the container is opaque, thereby limitingdegradation of the liquid by light.

The electrically heated smoking system may further comprise an atomizerincluding the at least one heating element. In addition to the heatingelement, the atomizer may include one or more electromechanical elementssuch as piezoelectric elements. Additionally or alternatively, theatomizer may also include elements that use electrostatic,electromagnetic or pneumatic effects.

The capillary wick may have a fibrous or spongy structure. For example,the capillary wick may comprise a plurality of fibers or threads,generally aligned in the longitudinal direction of the smoking system,or sponge-like material formed into a rod shape along the longitudinaldirection of the smoking system. The structure of the wick forms aplurality of small bores or tubes, through which the liquid can betransported from the liquid storage portion to the heating element, bycapillary action. The capillary wick may comprise any suitable materialor combination of materials. Examples of suitable materials are ceramic-or graphite-based materials in the form of fibers or sintered powders.The capillary wick may have any suitable capillarity and porosity so asto be used with different liquid physical properties such as density,viscosity, surface tension and vapor pressure.

The shell may comprise any suitable material or combination ofmaterials. Examples of suitable materials include metals, alloys,plastics or composite materials containing one or more of thosematerials. Preferably, the material is light and non-brittle.

The mouthpiece may comprise any suitable material or combination ofmaterials. Examples of suitable materials include thermoplastics thatare suitable for food or pharmaceutical applications, for examplepolypropylene, polyetheretherketone (PEEK) and polyethylene.

Preferably, the electrically heated smoking system is portable. Theelectrically heated smoking system may have a size comparable to aconventional cigar or cigarette.

According to a second aspect of the invention, there is provided amouthpiece for engaging with a shell to form an electrically heatedsmoking system, the shell having an electric power supply and electriccircuitry, the mouthpiece comprising: a liquid storage portion; acapillary wick having a first end and a second end, the first endextending into the liquid storage portion for contact with liquidtherein; at least one heating element for heating the second end of thecapillary wick; an air outlet; and an aerosol forming chamber betweenthe second end of the capillary wick and the air outlet, wherein, whenthe shell and mouthpiece are engaged, the at least one heating elementis in electrical connection with the power supply via the circuitry, anda flowpath or flow route for air is defined from at least one air inletto the air outlet via the aerosol forming chamber.

In a preferred embodiment, the at least one heating element comprises acoil of wire surrounding the second end of the capillary wick. In thatembodiment, preferably the wire is a metal alloy wire.

According to the invention, there is also provided a shell arranged toengage with the mouthpiece of the second aspect of the invention.

According to a third aspect of the invention, there is provided a shellfor engaging with a mouthpiece to form an electrically heated smokingsystem, the mouthpiece having a liquid storage portion, a capillary wickhaving a first end and a second end, the first end extending into theliquid storage portion for contact with liquid therein, at least oneheating element for heating the second end of the capillary wick, an airoutlet, and an aerosol forming chamber between the second end of thecapillary wick and the air outlet, the shell comprising: an electricpower supply; and electric circuitry, wherein, when the shell andmouthpiece are engaged, the at least one heating element is inelectrical connection with the power supply via the circuitry, and aflow route or flowpath for air is defined from at least one air inlet tothe air outlet via the aerosol forming chamber.

Preferably, the electric circuitry comprises a sensor to detect air flowindicative of a user taking a puff.

Preferably, the shell further comprises the at least one air inlet.

According to the invention, there is also provided a mouthpiece arrangedto engage with the shell of the third aspect of the invention.

Features described in relation to one aspect of the invention may alsobe applicable to another aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Many objects and advantages of the invention will be further described,by way of example only, with reference to the accompanying drawings, andothers will be apparent to those skilled in the art when theaccompanying drawings are read in conjunction with this writtendescription. In the accompanying drawings, like reference numerals areapplied to like elements and:

FIG. 1 shows a shell of an electrically heated smoking system accordingto an embodiment of the invention;

FIG. 2 shows a mouthpiece of an electrically heated smoking systemaccording to an embodiment of the invention; and

FIG. 3 shows a constructed electrically heated smoking system,comprising the shell of FIG. 1 and the mouthpiece of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a shell of an electrically heated smoking system accordingto one embodiment of the invention. The shell 101 comprises an electricpower supply in the form of battery 103, electric circuitry in the formof circuitry 105 and puff detection system 107, a puff indicator 109,electrical connections 111, electrical contacts 113, air inlets 115 anda lock mechanism 117. The shell 101 is designed to engage with themouthpiece 201 of FIG. 2.

FIG. 2 shows a mouthpiece of an electrically heated smoking systemaccording to one embodiment of the invention. The mouthpiece 201comprises a liquid storage portion in the form of cartridge 203containing liquid 205, a capillary wick 207, a heating element in theform of heating coil 209, an air outlet 211 and an aerosol formingchamber 213. The first end 207 a of the capillary wick 207 extends intothe cartridge 203 and the second end 207 b of the capillary wick 207 issurrounded by the heating coil 209. The mouthpiece also includes a cap215 to protect the second end 207 b of the capillary wick 207 and aninsulation ring 217. The mouthpiece 201 is designed to engage with theshell 101 of FIG. 1.

FIG. 3 shows the shell 101 of FIG. 1 engaged with the mouthpiece 201 ofFIG. 2 to form an electrically heated smoking system 301 arranged tosupply aerosol to a user on demand. The shell 101 and mouthpiece 201 arereleasably locked together by lock mechanism 117. Ends of the heatingcoil 209 are in contact with the electrical contacts 113 on the shell.Operation of the system 301 is as follows.

Liquid 205 is transferred from the cartridge 203 from the first end 207a of the wick 207 to the second end 207 b of the wick by capillaryaction. When the user draws on the device at the air outlet 211, ambientair is drawn through air inlets 115. In this embodiment, the puffdetection system 107 senses the puff and activates the heating coil 209and switches on the puff indicator 109. The battery 103 supplies a pulseof energy to the heating coil 209 to heat the second end 207 b of thewick 207. The liquid in the second end 207 b of the wick 207 isvaporized by the heating coil 209 to create a supersaturated vapor. Atthe same time, the liquid being vaporized is replaced by further liquidmoving towards the second end 207 b of wick by capillary action. (Thisis sometimes referred to as “pumping action”.) The supersaturated vaporcreated is mixed with and carried in the air flow from the air inlets115 towards the aerosol forming chamber 213. In the aerosol formingchamber 213, the vapor condenses to form an inhalable aerosol, which iscarried towards the outlet 211 and into the mouth of a user.

In this embodiment, the circuitry 105 and the puff detection system 107are programmable. The circuitry 105 and puff detection system 107 can beused to manage the device operation. In this embodiment, when the puffdetection system 107 senses the user taking a puff, the battery suppliesa current pulse of a pre-determined time to the heating coil 209. Thepre-determined time for the current pulse will depend on the amount ofliquid required for a single puff, and the time taken for that amount ofliquid to be vaporized. That will, in turn, depend on the properties ofthe liquid, the heating coil and the capillary wick. The pre-determinedtime may be between about 0.5 and about 3 seconds.

In this embodiment, the cartridge 203 in the mouthpiece is sized so asto contain sufficient liquid for a pre-determined number of puffs. Afterthat pre- determined number of puffs, the cartridge could be refilled,but preferably the entire mouthpiece is replaced. The pre-determinednumber of puffs is ideally between about 200 and about 2000 puffs andthis will depend on the desired size of the cartridge, mouthpiece andentire device, and the properties of the liquid being used. Thecartridge 203 can be made from any suitable material. Examples includeglass and plastic polymers such as PET or others used in thepharmaceutical or food industries. The material should be chosen so asto avoid leakage, breakage or abuse, as far as possible.

In the embodiment shown in FIGS. 1 to 3, when the shell and mouthpieceare engaged, the cartridge 203 is positioned upstream of the second end207 b of the wick and the heating coil 209. Thus, ambient air is drawnthrough air inlets 115 and passes around the cartridge 203 beforereaching the second end 207 b of the wick and the heating coil 209.However, in an alternative embodiment, the mouthpiece may be structuredsuch that, when the shell and mouthpiece are engaged, the cartridge ispositioned downstream of the second end of the wick and the heatingcoil. In that embodiment, the ambient air will be drawn through the airinlets, then the vapor or aerosol will pass around the cartridge on theway to the air outlet.

The capillary wick can be made from a variety of porous or capillarymaterials and preferably has a known, pre-defined capillarity. Examplesinclude ceramic- or graphite-based materials in the form of fibers orsintered powders. Wicks of different porosities can be used toaccommodate different liquid physical properties such as density,viscosity, surface tension and vapor pressure. The wick must be suitableso that the required amount of liquid can be delivered to the heatingcoil.

The mouthpiece and shell are sized and shaped so as to engage with oneanother, so as to produce a suitably sized electrically heated smokingsystem which can be used by a smoker. The components of the mouthpieceand shell, including the power supply, circuitry, liquid storageportion, wick, heating element and aerosol forming chamber areappropriately sized and shaped for the system design. The system ispreferably portable and may have a size similar to that of aconventional cigar or cigarette.

The system of the invention allows the control of particle concentration(milligrams per liter, mg/l or milligrams per puff volume, mg/puffvolume) in the aerosol, the average particle size in the aerosol and thedistribution (range) of particle sizes in the aerosol. These may becontrolled by varying one or more of: the aerosol former formulation inthe liquid, the energy transfer (thermal power per unit of surface area)at the heating element, the design of the aerosol forming chamber andthe operating temperature. The energy transfer will depend on a numberof factors including the materials used for the heating element and thewick, the diameter of the wick, the design of the heating elementincluding, if the heating element is a coil, the length, diameter andpitch (distance between spirals) of the coil, and the power applied tothe heating element.

The operating temperature should be controlled to ensure that, as far aspossible, no undesirable degradations of the aerosol former or formersand the flavouring material occur. This can be achieved, for example, bycontrolling the temperature of the heater if the heater is made from asuitable metal or alloy, using the variation in conductivity, or bycontrolling the amount of energy delivered to the heater. A preferredoperating temperature at the heating element is in the range of about100° to about 300° Celsius. The arrangement shown in the Figures canoperate within this temperature range, and may also provide a rapidresponse time (time between the user puffing on the system and theaerosol entering the user's mouth from the air outlet—this may bereferred to as “time to puff”) of between about 10 and about 500milliseconds, ms.

The word “about” is sometimes used in connection with numerical valuesto avoid an interpretation of those numerical values based onmathematical precision. Accordingly, when the word “about” is used witha numerical value that numerical value should be interpreted to includea tolerance of ±10% around the numerical value.

It is expressly intended that the various parts of this specification beinterpreted consistently with one another so as to preserve the full andfair breadth of the claimed invention, and not in a way to restrict thatinterpretation.

It will now be apparent to those skilled in the art that a new, useful,and nonobvious electrically heated smoking system has been described.Moreover, it will be apparent to those skilled in the art that numerousmodifications, variations, substitutions, and equivalents exist forvarious features of the invention. Accordingly, it is expressly intendedthat all such modifications, variations, substitutions, and equivalentsthat fall within the spirit and scope of the appended claims areembraced thereby.

What is claimed is:
 1. A mouthpiece for engaging with a shell to form anelectrically heated smoking system having an electric power supply andelectric circuitry, the mouthpiece comprising: a liquid storage portion;a capillary wick extending into the liquid storage portion for contactwith liquid therein; at least one heating element for heating thecapillary wick; an air outlet; and an aerosol forming chamber betweenthe capillary wick and the air outlet, wherein, when the shell andmouthpiece are engaged, the at least one heating element is inelectrical connection with the power supply via the circuitry, and aflowpath for air is defined from at least one air inlet to the airoutlet via the aerosol forming chamber.
 2. The mouthpiece of claim 1,wherein the at least one heating element comprises a coil of wiresurrounding the capillary wick.
 3. A shell arranged to engage with themouthpiece of claim
 1. 4. A shell for engaging with a mouthpiece to forman electrically heated smoking system, the mouthpiece having a liquidstorage portion, a capillary wick extending into the liquid storageportion for contact with liquid therein, at least one heating elementfor heating the capillary wick, an air outlet, and an aerosol formingchamber between the capillary wick and the air outlet, the shellcomprising: an electric power supply; and electric circuitry, wherein,when the shell and mouthpiece are engaged, the at least one heatingelement is in electrical connection with the power supply via thecircuitry, and a flow route for air is defined from at least one airinlet to the air outlet via the aerosol forming chamber.
 5. The shell ofclaim 4, wherein the electric circuitry comprises a sensor to detect airflow indicative of a user taking a puff.
 6. The shell of claim 4,further comprising the at least one air inlet.
 7. A mouthpiece arrangedto engage with the shell of claim
 4. 8. The electrically heated smokingsystem of claim 1, wherein air passes along an exterior of thecartridge.
 9. An electrically heated smoking system comprising: a shellhaving an electric power supply and electric circuitry; a liquid storageportion in the form of a cartridge which contains a liquid; a capillarywick extending into the cartridge for contact with the liquid therein;an air outlet; a heating element for heating a portion of the capillarywick; and an aerosol forming chamber between the capillary wick and theair outlet, wherein the shell and a mouthpiece are engaged at aconnection downstream of the liquid storage portion such that when theshell and the mouthpiece are engaged, the at least one heating elementis in electrical connection with the power supply via the electriccircuitry, and a flowpath for air is defined from at least one air inletto the air outlet via the aerosol forming chamber such that air isdirected into the aerosol forming chamber.